Flexible coupling with radially offset beams formed by asymmetric slot pairs

ABSTRACT

A flexible coupling for flexibly joining two shafts includes a unitary solid cylindrical body having a first end, a second end, and therebetween having one or more longitudinally spaced circular disks spaced by asymmetric slot pairs; a radially offset beam formed between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance R 1 ; each beam being rotationally offset from longitudinally adjacent beams; and hub means at the first end for coaxially connecting the first end to a first one of the two shafts, and hub means at the second end for coaxially connecting the second end to a second one of the two shafts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 60/325,429, filed Sep. 27, 2001 by Dennis G. Berg.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a flexible coupling for coupling two shafts, and more particularly to a flexible coupling with a slot-formed beam construction.

BACKGROUND OF THE INVENTION

The use of flexible couplings for interconnecting driving and driven shafts of precision instruments wherein the coupling is capable of accommodating shaft misalignments and axial shaft movements and permits limited torsional or radial deflection thereof is well known. In selected portions of an article entitled “Radial-Beam Couplings: A Cut Above the Rest” (Machine Design; Jul. 6, 2000) John B. Ricker states: “Of the many types available, single piece flexible couplings are the least expensive, and common geometries include radial slotted beam, helical or spiral, and bellows. The most critical factors to consider when choosing flexible couplings include torque capacity, torsional stiffness, bearing loads, transmission errors, shaft misalignment, and service life. Torque capacity is a measure of the coupler's amount of angular or parallel offset allowed from motor to load, and the life expectancy of the coupling. That is, stiff couplings operating under relatively high stress from large offsets can't survive millions of operating cycles. Transmission errors manifest themselves as small variations in velocity and position between motor and load. The variations are due primarily to coupling geometry and relative size. Bellows couplings usually provide the lowest transmission errors and radial bearing loads, good lateral flexibility, and the highest torsional stiffness. However, they have lower peak and running torque for equivalent sizes and are the most expensive. Bellows couplings have been traditionally used in smaller stepmotor and servomotor-driven systems. By comparison, helical or spiral couplings have sufficient lateral flexibility to handle large shaft offsets. But they also have only moderate torsional stiffness and the largest transmission errors. Helical couplings are generally categorized by the number of starting slots. For example, a single-beam helical coupling has one continuous cut throughout its entire one-piece flexing or working length. By contrast, a six-beam coupling has two sets of three helical cuts 120° apart separated by a center piece. A hub at each end of the coupling connects the motor drive shaft to the load, or feedback devices such as resolvers and encoders to lead screws and power transmission components. Ordinary radial beam slotted-type couplings fall between the above two types for cost, torsional stiffness, and transmission errors (driving an encoder), but produce the highest radial bearing load.”

An example of a helical flexible coupling is shown by U.S. Pat. No. 4,203,305 (Williams; 1980) which discloses a flexible coupling for torque transmission having a plurality of helical beams extending between the coupling ends.

An example of a radial beam slotted-type coupling is shown by U.S. Pat. No. 5,299,980 (Agius; 1994) which discloses a constant velocity flexible coupling for coupling two shafts that has a solid unitary body (22) with a plurality of complimentary pairs of slots (e.g., 34 paired with 36) positioned between a first and second end (hubs 24, 26). The plurality of complimentary pairs of slots extend inwardly from the circumference of the (cylindrical) body to a predetermined depth so as to form a plurality of beams (e.g., 46) between the complimentary pairs of slots. A plurality of disks (e.g., 111, 112) are formed in the body by the plurality of complementary pairs of slots, and the plurality of beams join and bridge the space between adjacent disks. Adjacent beams (e.g., 46, 64 or 78, 84) are angularly offset by a number of degrees (e.g., 90 degrees or e.g., 30 degrees). The illustrations (FIGS. 1–16) show that the “complimentary pairs of slots extending inwardly from the circumference of the body to a predetermined depth” form radial beams that are centered on diameters of the cylindrical beam, i.e., the “predetermined depth” is the same for each of the slots in a “complimentary pair of slots”.

As stated in the Ricker article hereinabove, radial beam slotted-type couplings fall between the bellows and helical types of flexible couplings in terms of cost, torsional stiffness, radial bearing load, and transmission errors. It is an object of the present invention to provide a novel flexible coupling that achieves performance advantages of both the bellows type and the slotted radial beam type while maintaining the low cost advantage of slot and beam types of flexible couplings.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a flexible coupling for flexibly joining two shafts comprises a unitary solid cylindrical body having a first end, a second end, and therebetween having one or more longitudinally spaced circular disks spaced by asymmetric slot pairs; a radially offset beam, having a minimum beam thickness T1 and a longitudinal beam length L1, formed between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance R1; each beam being rotationally offset from longitudinally adjacent beams; and hub means at the first end for coaxially connecting the first end to a first one of the two shafts, and hub means at the second end for coaxially connecting the second end to a second one of the two shafts.

According to the invention, the radial beam offset distance R1 is at least equal to or greater than a radius R2 of a coaxial shaft hole of the hub means at the first end or at the second end.

According to the invention, a rotational offset angle between longitudinally adjacent beams has the same magnitude for all pairs of longitudinally adjacent beams; and the rotational offset angle has a magnitude that divides into 360 degrees an integer number N times. Preferably the quantity of beams is an integer multiple of the number N. Also preferably the rotational offset angle increments in the same rotational direction from each beam to each beam's next longitudinally adjacent beam progressing from a first beam at the first end to a last beam at the second end. However, the rotational increment may vary and is not required to be the same.

According to the invention, all of the disks have a same nominal disk length (thickness) L3; and all of the first slots and all of the second slots have a same nominal slot length L2. Preferably the nominal disk length L3 is at least equal to, and may be greater than, a minimum value of the beam length L1.

According to the invention, the beam length L1 has a constant value for the entire beam.

According to the invention, the sides of the first slots and the sides of the second slots all have a single valued slot slope angle with respect to the plane of a radial slot centerline, wherein the slot slope angle has a value of up to 5 degrees. Preferably the slot slope angle has a value of up to 2 degrees.

According to the invention, each beam has a beam thickness that is uniformly equal to the minimum beam thickness T1 throughout a longitudinal length between adjacent disks.

According to the invention, each beam has a beam thickness that varies along a longitudinal length between adjacent disks, such that the minimum beam thickness T1 occurs in the approximate center of the longitudinal length, and the beam thickness increases from the minimum thickness T1 to a maximum where the beam joins a disk, with the increase being determined by rounded bottoms on the first slot and on the second slot of the asymmetric slot pair that formed the beam.

According to the invention, the hub means for coaxially connecting each of the first and second ends to one of the two shafts comprises a shaft hole with set screws, clamps or other means.

According to the invention, the two shafts are rotating members having potentially different axes of rotation. Alternatively, the two shafts are structural members that require flexible joining.

According to the invention, a method of flexibly joining two shafts with a flexible coupling, comprises the steps of: making the flexible coupling out of a unitary solid cylindrical body having a first end and a second end; forming a plurality of radially oriented asymmetric slot pairs longitudinally spaced from the first end to the second end; forming one or more circular disks longitudinally between asymmetric slot pairs; forming a radially offset beam between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance R1; rotationally offsetting each beam from longitudinally adjacent beams; and providing hub means at the first end for coaxially connecting the first end to a first one of the two shafts, and hub means at the second end for coaxially connecting the second end to a second one of the two shafts. The term “unitary” may include inserts affixed to or molded in the body.

Other objects, features and advantages of the invention will become apparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawing figures. The figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments.

Certain elements in selected ones of the drawings may be illustrated not-to-scale, for illustrative clarity. The cross-sectional views, if any, presented herein may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain background lines which would otherwise be visible in a true cross-sectional view, for illustrative clarity.

Elements of the figures can be numbered such that similar (including identical) elements may be referred to with similar numbers in a single drawing. By way of example not related to the present description, each of a plurality of elements collectively referred to as 199 may be referred to individually as 199 a, 199 b, 199 c, etc. Or, related but modified elements may have the same number but are distinguished by primes. By way of example not related to the present description, 199, 199′, and 199″ may be three different elements which are similar or related in some way, but have significant modifications, e.g., a member 199 having a static imbalance versus a similar but different member 199′ of the same design, but having a couple imbalance. Such relationships, if any, between similar elements in the same or different figures will become apparent throughout the specification, including, if applicable, in the claims and abstract.

The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view of a flexible coupling according to the invention, wherein the visible sides of radially offset beams are speckled for emphasis;

FIG. 2 is an exploded perspective view of the flexible coupling of FIG. 1 showing cross-sections of the beams between successive disks, according to the invention;

FIG. 3 is an end view of a cross-section through the first (right-hand) beam of FIGS. 1 and 2 showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 4 is an end view of a cross-section through the second beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 5 is an end view of a cross-section through the third beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 6 is an end view of a cross-section through the fourth beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 7 is an end view of a cross-section through the fifth beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 8 is an end view of a cross-section through the sixth beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 9 is an end view of a cross-section through the seventh beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 10 is an end view of a cross-section through the eighth beam from the right of FIGS. 1 and 2, showing radial offset and rotational angular positioning of the beam, according to the invention;

FIG. 11 is an end view of a flexible coupling with two beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 12 is an end view of a flexible coupling with three beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 13 is an end view of a flexible coupling with four beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 14 is an end view of a flexible coupling with five beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 15 is an end view of a flexible coupling with six beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 16 is an end view of a flexible coupling with seven beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 17 is an end view of a flexible coupling with eight beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 18 is an end view of a flexible coupling with nine beams hidden below an end hub, the beams indicated by dashed lines, showing radial offset and rotational angular positioning of the beams, according to the invention;

FIG. 19 is a side cross-sectional view of a beam between portions of two adjacent disks, showing an embodiment of the flexible coupling having sloped sides and rounded ends for the slots paired around the beam, according to the invention;

FIG. 19A is a side cross-sectional view of two adjacent beams between portions of three adjacent disks, showing an embodiment of the flexible coupling having sloped sides and rounded ends for the slots paired around each beam, according to the invention;

FIG. 20 is a side cross-sectional view of two adjacent beams between portions of three adjacent disks, showing an embodiment of the flexible coupling having non-sloped sides and square ends for the slots paired around each beam, according to the invention;

FIG. 21 is the cross-sectional end view of FIG. 3, showing dimensional characteristics of the beam relative to a hub with a shaft hole, according to the invention;

FIG. 21A is the cross-sectional end view of FIG. 4 superimposed on the view of FIG. 3, showing an angular relationship between the adjacent beams of the two views, according to the invention;

FIG. 22 is a perspective view of an embodiment of the flexible coupling having shaft hole and set screw means for coaxially connecting the flexible coupling to shafts, according to the invention; and

FIG. 23 is a perspective view of an embodiment of the flexible coupling having shaft hole and clamp means for coaxially connecting the flexible coupling to shafts, according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 10 (FIGS. 1–10) show a flexible coupling 108 that is an embodiment of the present invention having eight radially offset beams. The flexible coupling 108 has a unitary solid cylindrical body 14 with first and second ends 2 a, 2 b that are formed as hubs having means (e.g., coaxial shaft holes 4 a, 4 b) for coaxially connecting each of the first and second ends 2 a, 2 b to one of two shafts (not part of the invention, e.g., shafts 901, 903 outlined in FIG. 22) that are to be flexibly joined by the flexible coupling 108. One or more circular disks 6 a, 6 b, 6 c, 6 d, 6 e, 6 f, 6 g (collectively referred to as disks 6) are longitudinally spaced between the first and second ends 2 a, 2 b by asymmetric pairs of slots 10 a/11 a, 10 b/11 b, 10 c/11 c, 10 d/11 d, 10 e/11 e, 10 f/11 f, 10 g/11 g, 10 h/11 h (asymmetric slot pairs 10/11) forming radially offset beams 8 a, 8 b, 8 c, 8 d, 8 e, 8 f, 8 g, 8 h (collectively referred to as beams 8) therebetween. An axis of revolution AR for the cylindrical body 14 is shown extending through the length of the coupling 108. The shaft holes 4 a, 4 b, which are optionally of different diameters, are both coaxial to the axis of revolution AR and either shaft hole 4 a, 4 b optionally extends only through a corresponding end 2 a, 2 b, respectively, as shown, or optionally extends through at least some of the disks 6 and beams 8.

Referring to FIGS. 1, 2, and 3: longitudinally between a first end 2 a and a first disk 6 a, a first beam 8 a is formed between a first deep slot 10 a and a first shallow slot 11 a (a first asymmetric slot pair 10 a/11 a). Referring to FIGS. 1, 2, and 4: longitudinally between the first disk 6 a and a second disk 6 b, a second beam 8 b is formed between a second deep slot 10 b and a second shallow slot 11 b (a second asymmetric slot pair 10 b/11 b). Referring to FIGS. 1, 2, and 5: longitudinally between the second disk 6 b and a third disk 6 c, a third beam 8 c is formed between a third deep slot 10 c and a third shallow slot 11 c (a third asymmetric slot pair 10 c/11 c). Referring to FIGS. 1, 2, and 6: longitudinally between the third disk 6 c and a fourth disk 6 d, a fourth beam 8 d is formed between a fourth deep slot 10 d and a fourth shallow slot 11 d (a fourth asymmetric slot pair 10 d/11 d). Referring to FIGS. 1, 2, and 7: longitudinally between the fourth disk 6 d and a fifth disk 6 e, a fifth beam 8 e is formed between a fifth deep slot 10 e and a fifth shallow slot 11 e (a fifth asymmetric slot pair 10 e/11 e). Referring to FIGS. 1, 2, and 8: longitudinally between the fifth disk 6 e and a sixth disk 6 f, a sixth beam 8 f is formed between a sixth deep slot 10 f and a sixth shallow slot 11 f (a sixth asymmetric slot pair 10 f/11 f). Referring to FIGS. 1, 2, and 9: longitudinally between the sixth disk 6 f and a seventh disk 6 g, a seventh beam 8 g is formed between a seventh deep slot 10 g and a seventh shallow slot 11 g (a seventh asymmetric slot pair 10 g/11 g). Referring to FIGS. 1, 2, and 10: longitudinally between the seventh disk 6 g and a second end 2 b, an eighth beam 8 h is formed between an eighth deep slot 10 h and an eighth shallow slot 11 h (an eighth asymmetric slot pair 10 h/11 h).

An important feature of the present invention is a radial offset design for the beams 8. Referring to FIG. 21, various dimensions are shown for a view comparable to the cross-sectional views of FIGS. 3–10, but most closely representing the view of FIG. 3. The first beam 8 a is formed between the first deep slot 10 a and the first shallow slot 11 a, such that the first beam 8 a has a beam thickness T1. A beam centerline CL1 delineates the center of the beam thickness T1 along the entire length of the first beam 8 a. As shown in FIG. 21 for the first beam 8 a, typical of all the beams 8, the first beam 8 a (i.e., the beam centerline CL1) is parallel to a diameter DM of the cylindrical body 14, a portion of which is illustrated by the first end 2 a. Furthermore, the radially offset beam 8 (e.g., first beam 8 a) is offset from the parallel diameter DM by a non-zero radial beam offset distance R1. Thus the asymmetric slot pair 10/11 (e.g., first asymmetric slot pair 10 a/11 a) comprises a first deep slot 10 a with a deep slot depth D2 and a first shallow slot 11 a with a shallow slot depth D1 such that the deep slot depth D2 is greater than the shallow slot depth D1, preferably significantly greater. In a preferred embodiment illustrated by FIG. 21, the radial beam offset distance R1 is equal to a shaft hole radius R2 being the radius of at least one of the shaft holes 4 (e.g., 4 a). The slot depths D1 and D2 are measured from the beam 8 to an outer periphery of the body 14 along a diameter of the body 14 that is perpendicular to the beam 8 formed between the slots 11 and 10. Thus the slot depths D1 and D2 represent the greatest distance through the slots 11 and 10, respectively, measured perpendicularly from the beam 8 to the periphery of the body 14.

Compared to prior art radial beam designs, the radially offset beam design maintains excellent torsional and longitudinal stiffness, while enabling improved longitudinal bending flexibility for accommodating joined shafts that have angular and/or parallel misalignment. Each deep slot 10 is able to open wider since its paired shallow slot 11 pinches together much more due to a short pivot arm length D1. It can be seen that the radial beam design of the prior art, wherein the paired slot depths are equal and slightly less than the radius of the coupling, limits the amount of longitudinal flexing for a coupling with the same diameter as the present invention due to a relatively longer pivot arm length in any slot being pinched together.

As is readily apparent from the drawings, especially FIGS. 3–10, each beam 8 is rotationally offset from any adjacent beam. Referring to FIGS. 21 and 3, the first beam 8 a is positioned at a first rotational angle α relative to an arbitrary axis labeled “x” that is orthogonal to an axis of rotation AR of the end hub 2 a. The axis of rotation AR is therefore also the axis of rotation of both ends 2, of all disks 6, and of the cylindrical body 14 of the flexible coupling 108 as shown in FIGS. 1 and 2. From FIG. 4 it can be seen that the next adjacent beam, the second beam 8 b, is rotated clockwise to a second rotational angle α′ (not shown). Likewise, from FIG. 5 it can be seen that the next adjacent beam, the third beam 8 c, is rotated clockwise to a third rotational angle α41 (not shown). The rotation of the beams 8 continues from each beam to each adjacent beam. The difference in rotational angles α between adjacent beams 8 is a rotational offset angle β. FIG. 21A illustrates an example of the rotational offset angle β shown between the first beam 8 a and the adjacent second beam 8 b. Since the beams 8 are radially offset, it is convenient to measure the rotational offset angle β between diameters DMa and DMb that are parallel to the beams 8 a and 8 b, respectively. For the sake of uniformity in flexing as the coupling 108 is rotated, preferably the rotational offset angle β has the same magnitude for all of the adjacent beams 8 such that the rotational offset angle β has a magnitude that divides into 360° an integer number N times. Most preferably, the number of beams is an integer multiple of the number N. Also preferably the rotational offset angle β increments in the same rotational direction as measured from the first beam 8 a to the adjacent second beam 8 b, from the second beam 8 b to the adjacent third beam 8 c, and so on from each beam to its next adjacent beam progressing from the first beam (e.g., first beam 8 a) to a last beam (e.g., eighth beam 8 h). For example, the flexible coupling 108 has eight radially offset beams 8 having a single rotational offset angle β of 45°, which is 360° divided by the integer number N=8. For example, the preferred design rules would also be satisfied if there were two times eight beams 8 (16 beams) having a rotational offset angle β of 45°, which is 360° divided by eight, resulting in a flexible coupling that has twice the flexible length of the flexible coupling 108.

A variety of flexible couplings can be constructed according to the present invention. FIGS. 11 through 18 (FIGS. 11–18) illustrate designs having from two beams 8 to nine beams 8. The designs in FIGS. 11–18 are only examples, since any number of beams 8 is possible. Each of the FIGS. 11–18 shows an end view of a coupling wherein the underlying beams 8 are shown with dashed lines indicating that the beams 8 are hidden under an end hub 2 having a shaft hole 4. FIG. 11 shows a coupling 102 having two beams 8 a, 8 b that are uniformly rotationally offset by a rotational offset angle β of magnitude 180° (360° divided by 2). FIG. 12 shows a coupling 103 having three beams 8 a, 8 b, 8 c that are uniformly rotationally offset by a rotational offset angle β of magnitude 120° (360° divided by 3). FIG. 13 shows a coupling 104 having four beams 8 a, 8 b, 8 c, 8 d that are uniformly rotationally offset by a rotational offset angle β of magnitude 90° (360° divided by 4). FIG. 14 shows a coupling 105 having five beams 8 a, 8 b, 8 c, 8 d, 8 e that are uniformly rotationally offset by a rotational offset angle β of magnitude 72° (360° divided by 5). FIG. 15 shows a coupling 106 having six beams 8 a, 8 b, 8 c, 8 d, 8 e, 8 f that are uniformly rotationally offset by a rotational offset angle β of magnitude 60° (360° divided by 6). FIG. 16 shows a coupling 107 having seven beams 8 a, 8 b, 8 c, 8 d, 8 e, 8 f, 8 g that are uniformly rotationally offset by a rotational offset angle β of magnitude 51.4° (360° divided by 7). FIG. 17 shows a coupling 108 (equivalent to the coupling 108 shown in FIGS. 1 and 2) having eight beams 8 a, 8 b, 8 c, 8 d, 8 e, 8 f, 8 g, 8 h that are uniformly rotationally offset by a rotational offset angle β of magnitude 45° (360° divided by 8). FIG. 18 shows a coupling 109 having nine beams 8 a, 8 b, 8 c, 8 d, 8 e, 8 f, 8 g, 8 h, 8 i that are uniformly rotationally offset by a rotational offset angle β of magnitude 40° (360° divided by 9).

Increasing the number of beams 8 produces increasingly flexible couplings. A smaller rotational offset angle β between adjacent beams 8 results in a smoother transition for the torsional loading of adjacent beams. For example, the coupling 109 having nine beams 8 with a 40° rotational offset angle β, is much more longitudinally flexible than the coupling 102 having only two beams 8 with a 180° rotational offset angle β.

It is within the scope of the present invention to have different cross-sectional profiles for the slots 10, 11. For illustrative simplicity, the views of FIGS. 1 through 18 and 21 and 21A show squared-off profiles for the slots 10, 11. For example, the cross-sectional view of FIG. 20 shows a portion of the coupling 108 with a squared-off profile. The deep slots 10 (e.g., 10 b,10 c) each have straight (non-sloping) sides 120, and the paired shallow slots 11 (e.g., 11 b, 11 c) each have straight (non-sloping) sides 121. The beams 8 (e.g., 8 b, 8 c) each have a beam length L1 (nominal beam length L1) measured longitudinally between adjacent disks 6 (e.g., disk 6 a to disk 6 b, or disk 6 b to disk 6 c); and the beam length L1 is constant for the entire beam 8 (e.g., 8 b, 8 c). The beams 8 (e.g., 8 b, 8 c) each have a beam thickness T1 measured between bottoms of paired slots 10/11 (e.g., bottom of shallow slot 11 b to bottom of deep slot 10 b, or bottom of deep slot 10 c to bottom of shallow slot 11 c); and the beam thickness T1 is constant for the entire beam 8 (e.g., 8 b, 8 c). Measured at an outer periphery of the coupling 108, the deep slots 10 (e.g., 10 b, 10 c) each have a length L4 that is constant for the entire deep slot 10, and therefore equals the beam length L1. Also measured at an outer periphery of the coupling 108, the shallow slots 11 (e.g., 11 b, 11 c) each have a length L2 that is constant for the entire shallow slot 11, and therefore equals the beam length L1 and thus the deep slot length L4. Finally, measured at the axis of revolution AR, the disks 6 (e.g., disk 6 b) each have a length L3 (nominal disk length L3) that is constant for the entire disk 6.

The disk length L3, beam length L1 (equaling slot lengths L2, L4), slot depths D1, D2, and beam thickness T1 can be adjusted to match physical characteristics (e.g., bending stress limit) of the material used for the body 14 with physical demands (e.g., shaft misalignment angle) of an application for the coupling 108. Preferably the coupling 108 has a disk length L3 that is equal to the beam length L1 (and slot lengths L2, L4), and that is also equal to the beam thickness T1.

A preferred cross-sectional profile for slots 410, 411 (compare slots 10, 11) is illustrated in FIGS. 19 and 19A which show cross-sectional views of portions of a preferred sloped-slot design for a flexible coupling 108′ (compare 108). The deep slots 410 (e.g., 410 b, 410 c) each have sides 420 that slope with a slot slope angle φ (opening outward as measured from a slot centerline CL2 to the deep slot side 420), preferably from 0° to 5°, and most preferably from 0° to 2°. Likewise, the paired shallow slots 411 (e.g., 411 b, 411 c) each have sides 421 that slope with a slot slope angle φ (opening outward as measured from the slot centerline CL2 to the shallow slot side 421), preferably from 0° to 5°, and most preferably from 0° to 2°. Also preferably, the slot slope angle φ has the same magnitude for the deep slots 410 and for the shallow slots 411.

In its simplest form, parallel-sided slots 410/411 open outward with the planes of a plurality of slot slope angles φ all being oriented normal to the entire beam 408, i.e., normal to all points of the beam centerline CL1 (see both FIGS. 19 and 21). However, it is within the scope of the present invention to have fan-sloped slots 410/411 wherein the slot slope angle φ is oriented in a plurality of planes that fan around like radii from a point at the intersection of the beam centerline CL1 and a diameter DMx that is normal to the beam centerline CL1.

An optional, but preferred profile for the sloped slots 410/411 includes slot bottoms 430/431 that are rounded with a radius of curvature RC1.

The beams 408 (e.g., 408 b, 408 c) each have a beam length L1 between adjacent disks 406 (e.g., disk 406 a to disk 406 b, or disk 406 b to disk 406 c) that is measured longitudinally through a beam centerline CL1. The beams 408 (e.g., 408 b, 408 c) each have a beam thickness T1 measured along the slot centerline CL2 between bottoms (optionally rounded bottoms 430/431) of paired slots 410/411 (e.g., bottom of shallow slot 411 b to bottom of deep slot 410 b, or bottom of deep slot 410 c to bottom of shallow slot 411 c). If the bottoms of the slots 410/411 are flat, then the beam thickness T1 is constant for the entire beam 408; but if the rounded bottoms 430/431 are used, then the beam thickness T1 varies along the length L1 of the beam 408 (e.g., 408 b, 408 c), and has a minimum beam thickness T1 at the slot centerline CL2. If parallel-sided slots 410/411 are used, then the beam length L1 is constant for the entire beam 408; but if fan-sloped slots 410/411 are used, then the beam length L1 varies along the entire beam 408, having a minimum beam length L1 at the point at the intersection of the beam centerline CL1 and the diameter DMx.

Measured at an outer periphery of the coupling 108′, the deep slots 410 (e.g., 410 b, 410 c) each have a length L4, and a depth D2 measured along the diameter DMx that is normal to the beam centerline CL1. If parallel-sided slots 410/411 are used (see FIG. 20), then the deep slot length L4 is constant around the periphery of the deep slots 410; but if fan-sloped slots 410/411 are used (see FIGS. 19 and 19A), then the deep slot length L4 varies around the periphery of the deep slots 410.

Also measured at an outer periphery of the coupling 108′, the shallow slots 411 (e.g., 411 b, 411 c) each have a length L2, and a depth D1 measured along the diameter DMx that is normal to the beam centerline CL1. If parallel-sided slots 410/411 are used, then the shallow slot length L2 is constant around the periphery of the shallow slots 411; but if fan-sloped slots 410/411 are used, then the shallow slot length L2 varies around the periphery of the shallow slots 411. As a result of the slot slope angle φ being preferably equal for the deep slots 410 and for the shallow slots 411, it can be seen that a slot length measured at a shallow slot depth D1 in the deep slot 410 will have the same magnitude as the shallow slot length L2, therefore the length L2 can also be a “nominal slot length L2” that is used to indicate a longitudinal length for all slots 10 and 11, i.e., for both the deep slots 10 and the shallow slots 11, regardless of slot profile.

Finally, measured at the axis of revolution AR, the disks 406 (e.g., disk 406 b) each have a nominal disk length L3. As detailed hereinabove, the longitudinal length at any given location on a disk 406 is generally variable and is highly dependent on the magnitude of the slot slope angle φ and on the orientation of the plane of the slot slope angle φ where it passes through the given location.

The nominal disk length L3, beam length L1, slot lengths L2, L4, slot depths D1, D2, beam thickness T1, slot slope angle φ and choice of parallel-sided or fan-sloped slots can be adjusted to match physical characteristics (e.g., bending stress limit) of the material used for the body 414 with physical demands (e.g., shaft misalignment angle) of an application for the coupling 108′.

With reference to FIGS. 22 and 23, the two shafts (not part of the invention, e.g., 901, 903) that are to be flexibly joined by a flexible coupling 208, 308 (compare 108 and 108′) are fitted into suitably sized shaft holes 204, 304 (e.g., 204 a, 304 a, compare 4 a, 4 b). One shaft hole 204 (e.g., 204 a) is coaxially formed in each end 202 a, 202 b of the coupling 208, the ends 202 a, 202 b being hubs having means for coaxially connecting each of the ends 202 a, 202 b to a respective one of the two shafts 901, 903. One shaft hole 304 (e.g., 304 a) is coaxially formed in each end 302 a, 302 b of the coupling 308, the ends 302 a, 302 b being hubs having means for coaxially connecting each of the ends 302 a, 302 b to a respective one of the two shafts 901, 903. The suitably sized holes 204, 304 have cross-sectional profiles that fit the dimensions and shape of the cross-sectional profiles of the respective shaft 901, 903. For example, the cross-sectional profiles can be circular (as shown) with diameters that may or may not be the same for the two shafts 901, 903. For example, the cross-sectional profiles can be D-shaped or hexagonal.

FIG. 22 illustrates a first preferred means for coaxially connecting each of the ends 202 a, 202 b to a respective one of the two shafts 901, 903 using one or more set screws 252 screwed into corresponding threaded set screw holes 250 such that the one or more set screws 252 in an end (e.g., 202 a) press into the shaft (e.g., 901) fitted into the respective shaft hole (e.g., 204 a).

FIG. 23 illustrates a second preferred means for coaxially connecting each of the ends 302 a, 302 b to a respective one of the two shafts 901, 903 using clamps 360 a, 360 b, respectively. The clamps 360 a, 360 b each comprise a radial clamping slit 356 a, 356 b that divides a first clamp side 354 a, 354 b from a second clamp side 358 a, 358 b. The clamping slit 356 a, 356 b must not be crossed by a beam in order to assure that at least one of the first and second clamp sides (354 a and 358 a, or 354 b and 358 b) is free to move against the other, thereby clamping the shaft 901, 903 in its respective end hub 302 a, 302 b. The clamping action is accomplished, for example, by a screw 352 in a hole 350 that is threaded only in the first clamp side 354 a, 354 b.

Any suitable material can be used for the body (e.g., 14) of the flexible couplings (e.g., 108) according to the present invention, but preferably the material is low density (for light weight, low inertia), and resistant to ultraviolet/moisture/oil/fuel/solvent. For example, preferred suitable materials are high performance aluminum alloys or engineered plastics. Use of engineered plastics adds the advantage of being electrically nonconductive.

Although the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character—it being understood that only preferred embodiments have been shown and described, and that all changes and modifications that come within the spirit of the invention are desired to be protected. Undoubtedly, many other “variations” on the “themes” set forth hereinabove will occur to one having ordinary skill in the art to which the present invention most nearly pertains, and such variations are intended to be within the scope of the invention, as disclosed herein. 

1. A flexible coupling for flexibly joining two shafts, the flexible coupling comprising: a unitary solid cylindrical body having a first end, a second end, and therebetween having one or more longitudinally spaced circular disks spaced by asymmetric slot pairs; a radially offset beam, having a minimum beam thickness (T1) and a longitudinal beam length (L1), formed between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance (R1); each beam being rotationally offset from longitudinally adjacent beams; and means at the first end for coaxially connecting the first end to a first one of the two shafts, and means at the second end for coaxially connecting the second end to a second one of the two shafts.
 2. The flexible coupling of claim 1, wherein: the radial beam offset distance (R1) is approximately equal to the largest of a radius (R2) of a coaxial shaft hole of the means at the first end or at the second end.
 3. The flexible coupling of claim 1, wherein: a rotational offset angle between longitudinally adjacent beams has the same magnitude for all pairs of longitudinally adjacent beams; and the rotational offset angle has a magnitude that divides into 360 degrees an integer number N times.
 4. The flexible coupling of claim 3, wherein: the quantity of beams is an integer multiple of the number N.
 5. The flexible coupling of claim 3, wherein: the rotational offset angle increments in the same rotational direction from each beam to each beam's next longitudinally adjacent beam progressing from a first beam at the first end to a last beam at the second end.
 6. The flexible coupling of claim 1, wherein: all of the disks have a same nominal disk length (L3); and all of the first slots and all of the second slots have a same nominal slot length (L2,L4).
 7. The flexible coupling of claim 6, wherein: the nominal disk length (L3) is equal to the nominal slot length (L2).
 8. The flexible coupling of claim 6, wherein: the nominal disk length (L3) is equal to a minimum value of the beam length (L1).
 9. The flexible coupling of claim 1, wherein: the beam length (L1) has a constant value for the entire beam.
 10. The flexible coupling of claim 1, wherein: each beam has a beam thickness that is uniformly equal to the minimum beam thickness (T1) throughout a longitudinal length between adjacent disks.
 11. The flexible coupling of claim 1, wherein: each beam has a beam thickness that varies along a longitudinal length between adjacent disks, such that the minimum beam thickness (T1) occurs in the approximate center of the longitudinal length, and the beam thickness increases from the minimum thickness (T1) to a maximum where the beam joins a disk, with the increase being determined by rounded bottoms on the first slot and on the second slot of the asymmetric slot pair that formed the beam.
 12. The flexible coupling of claim 1, wherein: the means for coaxially connecting each of the first and second ends to one of the two shafts comprises hub means.
 13. The flexible coupling of claim 1, wherein: the means for coaxially connecting each of the first and second ends to one of the two shafts comprises hub means with a shaft hole with at least one set screw.
 14. The flexible coupling of claim 1, wherein: the means for coaxially connecting each of the first and second ends to one of the two shafts comprises hub means with a shaft hole and at least one clamp.
 15. The flexible coupling of claim 1, wherein: the two shafts are rotating members having potentially different axes of rotation.
 16. The flexible coupling of claim 1, wherein: the two shafts are structural members that require flexible joining.
 17. A flexible coupling for flexibly joining two shafts, the flexible coupling comprising: a unitary solid cylindrical body having a first end, a second end, and therebetween having one or more longitudinally spaced circular disks spaced by asymmetric slot pairs; a radially offset beam, having a minimum beam thickness (T1) and a longitudinal beam length (L1), formed between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance (R1); each beam being rotationally offset from longitudinally adjacent beams; and means eat the first end for coaxially connecting the first end to a first one of the two shafts, and means at the second end for coaxially connecting the second end to a second one of the two shafts, and wherein the sides of the first slots and the sides of the second slots all have a single valued slot slope angle with respect to the plane of a radial slat centerline, wherein the slot slope angle has a value of up to 5 degrees.
 18. The flexible coupling of claim 17, wherein: the slot slope angle has a value of up to 2 degrees.
 19. A method of flexibly joining two shafts with a flexible coupling, comprising the steps of: making the flexible coupling out of a unitary solid cylindrical body having a first end and a second end; forming a plurality of radially oriented asymmetric slot pairs longitudinally spaced from the first end to the second end; forming one or more circular disks longitudinally between asymmetric slot pairs; forming a radially offset beam between a first slot and a second slot of each asymmetric slot pair, such that the radially offset beam is parallel to a diameter of the cylindrical body and is offset from the parallel diameter by a radial beam offset distance R1; rotationally offsetting each beam from longitudinally adjacent beams; and providing means at the first end for coaxially connecting the first end to a first one of the two shafts, and means at the second end for coaxially connecting the second end to a second one of the two shafts. 